1. Field of the Invention
This invention relates to dihydrofuran derivatives and, more specifically, to certain substituted-2,3-dihydrofurans which are useful fragrance compounds.
2. Description of the Prior Art
The use of synthetic fragrance chemicals has added a new dimension to the art of perfumery. As a result of the development of new synthetic perfume chemicals, perfumers have greater flexibility in developing fragrance formulations and are better able to mimic natural aromas. However, as perfumers become more adept in the use of synthetic materials for the formulation of sophisticated fragrances and developing the subtle nuances typically associated with natural fragrances, there is a growing demand for new synthetic fragrance compounds.
Furan derivatives are known to have desirable fragrance and flavor qualities. For example, ethyl furoate, n-amyl furoate, ethyl furyl beta-hydroxypropionate and furfural are reported as being useful for the formulation of perfumes, cosmetics and soaps. Furfuryl alkyl and aryl ethers are disclosed as flavor enhancers in U.S. Pat. No. 3,940,502.
Tetrahydrofurans are also disclosed to be useful for fragrance applications. U.S. Pat. No. 3,668,134, for example, discloses the use of esters/ethers of tetrahydrofurans as perfumery ingredients for detergent compositions. 3-Oximino-4-oxo-2,5-dimethyltetrahydrofuran is described in U.S. Pat. No. 4,116,982 and disclosed to have a fine caramel-like fragrance making it useful for the manufacture of scents and flavors. 2-Acetonyl-3,5-dimethyl-5-isopropyltetrahydrofuran is disclosed in U.S. Pat. No. 3,470,209 as having a pleasant spicy odor reminiscent of bay and eucalyptus. 2-(1'-Hydroxymethyl-ethyl)-5-methyl-5-vinyltetrahydrofuran is disclosed in U.S. Pat. No. 3,764,567 to be a useful for floral perfumes. In U.S. Pat. No. 3,227,731 carbonates of 1-(alpha-furyl)-2,2-dialkyl-1,3-dihydroxypropanes and 1-(alpha-tetrahydrofuryl)-2,2-dialkyl-1,3-dihydroxypropanes are indicated to be useful in perfume compounding.
2,3-Dihydrofurans having a vinyl group at the 2-position, a lower carboxylate radical at the 4-position and a methyl group at the 5-position have been reported in Chemical Abstracts, Volume 75, 87758y (1971): Volume 93, 71095r (1980): Volume 93, 239112v (1980): and Volume 94, 15458v (1981). Dihydrofurans of the same general type are also reported by Vinogradov et. al. in Izv. Akad. Nauk SSSR Ser. Khimm, 1981, (9), 2077-84 and Morlyan et. al. in Russian Patent (Inventor's Certificate) No. 979,346. The compounds of Vinogradov et. al. and Morlyan et. al. are obtained by the oxidative addition of 1,3-dicarbonyl compounds with dienes in acetic acid and in the presence of manganese (III) acetate and copper (II) acetate. Employing a similar reaction procedure, Heiba et. al. (J. Chem Vol., Vol. 39, No. 23, 1974) have prepared and reported 2,3-dihydrofurans having a phenyl group substituted at the 2-position.